The present invention is concerned with a monolithic semiconductor integrated circuit for television receivers.
A signal processing circuit formed in a monolithic semiconductor integrated circuit for television receivers has been known, for example, in IEEE JOURNAL OF SOLID-STATE CIRCUITS, Vol. SC-4, No. 4, pp. 202-210, published in August, 1969.
On the outer side of the monolithic semiconductor integrated circuit have been arrayed a tuner, a video intermediate-frequency amplifier, and a video detector. The video intermediate-frequency output signals obtained from the tuner are amplified by the video intermediate-frequency amplifier, and the output of the video intermediate-frequency amplifier is applied to the input of the video detector. The detected signals produced by the video detector are fed to the input of a video amplifier in the monolithic semiconductor integrated circuit. The video output signals of the video amplifier in the integrated circuit are fed to the input of a sync separator in the integrated circuit. The outputs of the sync separator are fed to a vertical oscillation output circuit and to a horizontal oscillation output circuit.
In developing a monolithic semiconductor integrated circuit for television receivers, having a video intermediate-frequency amplifier, a video detector, a sync separator and the like formed in a single semiconductor chip, the inventors of the present invention have encountered the below-mentioned difficulty.
The output response of a sync separator circuit in a television receiver takes the form of sharp pulse-like waveforms, and has great output voltage. Therefore, if a high-frequency amplifier circuit such as video intermediate-frequency amplifier and the sync separator circuit are constructed in the form of a single monolithic semiconductor integrated circuit, harmonic components of the sync pulse are fed back to the high-frequency amplifier circuit, giving rise to the occurrence of oscillation and crosstalk. To prevent such inconveniences, therefore, the high-frequency high-gain circuit and the sync separator circuit had to be constructed in the form of separate monolithic semiconductor integrated circuits.